A way to leave USB power on during standby

Ok, I haven't had a new laptop in a while so perhaps this already happens, but I'm now carrying more devices that can charge off the USB power, including my cell phone. It's only 2.5 watts, but it's good enough for many purposes.

However, my laptops, and desktops, do not provide USB power when in standby or off. So how about a physical or soft switch to enable that? Or even a smart mode in the US that lets you list what devices you want to keep powered and which ones you don't? (This would probably keep all devices powered if any one such device is connected, unless you had individual power control for each plug.)

This would only be when on AC power of course, not on battery unless explicitly asked for as an emergency need.

To get really smart a protocol could be developed where the computer can ask the USB device if it needs power. A fully charged device that plans to sleep would say no. A device needing charge could say yes.

Of course, you only want to do this if the power supply can efficiently generate 5 volts. Some PC power supplies are not efficient at low loads and so may not be a good choice for this, and smaller power supplies should be used.

As a nomadic rather than mobile user, I am strongly in favor of a laptop that uses external power. The battery is a significant portion of the weight of the laptop and I don't use it (unless I accidentally jostle the power cord).

So I'd like to see (for laptops and desktops) an external power supply.

Power supplies also generate most of the heat in a laptop (the rest comes from the CPU, I think).

Hey Brad... just across this randomly. Thought I'd mention, this is available now in some ThinkPads from Lenovo. There's a yellow USB port which can draw out power from the AC adapter without waking the computer at all. And i think the newer models like T400S can drain the battery power to power another device when AC is not present (and the laptop is off)! Pretty darn cool!!